How to find the rafter length with a 5/12 pitch and a 6 inch over hang. The dog house is 3 ft wide by 4 ft long

Run is 1/2 the width plus the over hang.
(36/2)+6=24
Rise is 5" for ever 12" run or 10"
Rafter length = A squared plus B squared = C squared
(24x24)+(10x10)=676
Sq rt of 676=26"

If you are using a ridge board subtract 1/2 thickness of ridge board from run.
2x4 ridge board=
(23.25x23.25)+(10x10)=640.56
Sq rt of 640.56=25.31=25 and 7/16